1. Field of the Invention
The invention relates to a backup locking system for a thrust reverser door, which system is intended to hold said door in the event of failure of its main locking means, said system comprising a catch mounted so that it can pivot about a first pivot pin on a fixed structure of the thrust reverser between a closed position and an open position and having, at its free end, a hook arranged in a plane perpendicular to said first pivot pin and adapted to cooperate, when said door is in its closed position, with a locking interface secured to said door, and said system also comprising means for keeping said catch against said interface when said door is in its closed position, means for effecting opening of said catch, and means for automatically closing said catch, actuated by said door as it moves toward its closed position.
Turbine engines fitted to aircraft may include thrust reversers which make it possible to reverse the direction of a stream of propulsion gases generated by the turbine engines so as to slow the aircraft down.
These thrust reversers comprise a fixed annular structure surrounding the turbine engine and through which a number of radial openings pass, and movable shutters, also known as doors, capable of closing the radial openings. In a forward thrust configuration, the radial openings are closed, and the stream of propulsion gases generated by the turbine engine is routed toward the rear so as to propel the aircraft. In a reverse thrust configuration, the radial openings are open, the movable shutters or doors are pivoted to the rear and at least partially shut off the gaseous stream flow duct, and the stream of gases comes out through the openings and is directed toward the front of the turbine engine so as to slow the aircraft down. A great deal of safety is required in keeping the doors in the closed position.
The doors are actuated by rams and are kept closed by a main locking system. A backup locking system is provided for the purpose of keeping the door closed in the event of failure of the main locking system, and it is to this backup locking system that the invention relates.
2. Summary of the Prior Art
FR-A-2 765 916 represents the state of the art closest to the invention, and discloses, in FIGS. 17 and 18, a backup locking system which comprises a catch ending in a hook and constantly urged closed by resilient means, means for opening the catch consisting of a ram which moves the catch toward a position of maximum opening, and a spring-loaded keeper intended to keep the catch in the open position. During the door closure movement, the door displaces the keeper to release the catch so that it is returned to the closed position by the reslient means. The keeper comprises a retractable stop against which a mating stop of the catch is able to bear so as to keep the catch in the open position. When the door opens, the keeper is urged by its spring so that the retractable stop lacates under the mating stop once the catch has been opened. When the ram is depressurized, the catch returns backward under the action of the resilient forces and the keeper is set. In the event of wear on the stop and on the mating stop, the catch may close itself prematurely under the action of the resilient means and may prevent subsequent closure of the door.
It is an object of the invention to provide a locking system as mentioned earlier, in which the catch can close only under the action of automatic closure means actuated by the door during its closure movement.
Accordingly the invention provides a backup locking system for a door of a thrust reverser, which system is intended to hold said door in the event of failure of its main locking means, said system comprising:
a catch mounted so that it can pivot about a first pivot pin on a fixed structure of said thrust reverser between a closed position and an open position, said catch having a free end provided with a hook arranged in a plane perpendicular to said first pivot pin and adapted to cooperate, when said door is in a closed position, with a locking interface secured to said door, and said catch further having a heel at its end remote from said hook, said heel having a lateral face and a part-cylindrical surface centered on the axis of said first pivot pin;
retaining means for keeping said catch against said locking interface when said door is in its closed position;
means for effecting opening of said catch; and
means for automatically closing said catch, said means being actuated by said door as it moves toward its closed position;
said retaining means comprising a cylinder secured to said fixed structure, a piston slidably mounted in said cylinder, a piston rod secured to said piston and having an end facing said heel of said catch, and resilient means acting on said piston to urge the end of said piston rod against said lateral face of said heel when said catch is in its closed position; and
said means for effecting opening of said catch comprise:
means for permitting the supply of a pressurized fluid to said cylinder to act on said piston in opposition to said resilient means so as to retract said end of said piston rod away from said heel, and
means for causing said catch to pivot through at least a minimum opening angle when said piston rod is retracted away from said heel so as to allow the opening of said door, the end of said piston rod facing said part-cylindrical surface of said heel when said catch reaches said minimum opening angle.
Thus, the action of the resilient means is canceled while the piston is being acted upon by the pressurized fluid, and this has the effect of opening the catch to a minimum opening angle, in which position the piston rod faces the part-cylindrical surface of the heel. When the pressurized fluid in the cylinder is released, the end of the piston rod will be pressed against the part-cylindrical surface of the heel by the resilient means, but will not be able to cause inadvertent closure of the catch.
Advantageously, the means for causing the catch to pivot through a minimum opening angle comprise a double opening lever mounted to pivot about a second pivot pin secured to the fixed structure and parallel to the first pivot pin, this double lever being articulated at a first end on the piston rod and having a free end capable of pushing the catch away from said closed position as a result of the retraction of the piston rod. Thus, the catch is opened positively by the ram.
These means may further comprise an unlocking spring inserted between the catch and the fixed structure. In this case, the resilient means provided in the ram exerts on the catch a torque which opposes and exceeds the torque exerted by the unlocking spring.
Thus, the means for causing the catch to pivot through at least a minimum opening angle are redundant, as a safety measure.
As a preference, said means of automatically closing said catch comprise a closure lever having two ends and mounted to pivot at one of its ends on a third pivot pin secured to said fixed structure and parallel to said first pivot pin, this closure lever being connected to said catch by a link rod, the free end of said closure lever lying in the path of a fitting secured to said door and intended to actuate said lever during a final phase of closure of said door so as to return said catch to said closed position.
If an unlocking spring is provided, then this spring opens said catch to a maximum position of opening, when said fitting moves away from said free end of said closure lever as the door is being opened.
The position of maximum opening is defined by a mechanical stop provided on the closure lever. In this position of maximum opening, the head of the piston rod presses against the part-cylindrical surface of the heel when the ram is depressurized. The resilient means are then inoperative. When the door is closed, the fitting actuates the closure lever and this returns the catch to the closed position. The head of the piston rod slides along the part-cylindrical surface and when it reaches the lateral face of the heel, the resilient means act to apply the catch against the locking interface.